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How to Trace Federal Legislation – A Research Guide

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Any given provision in the current U.S. Code may be the product of multiple acts passed over a long period of time. So, how do you unpack the provision and discover the different acts that gave rise to a particular section of the Code? Tracing legislation from the Code back to the bills, public laws, and Statutes at Large that created it may seem daunting for the uninitiated, but we hope this research guide will help simplify the process.

[Lobby to Main Reading Room. Good Legislation mural by Elihu Vedder. Library of Congress Thomas Jefferson Building, Washington, D.C.]
“Lobby to Main Reading Room. Good Legislation mural by Elihu Vedder. Library of Congress Thomas Jefferson Building, Washington, D.C.” courtesy of the Prints and Photographs Division, Library of Congress
Beginning Your Search with the United States Code and Source Credits

The first step in tracing a piece of legislation will be to look at the United States Code (“U.S. Code”) section of interest in a print or online resource.  For more information about where to find the U.S. Code in print and online, we suggest reviewing our previous post, “Federal Statutes: A Beginner’s Guide,” particularly the “The United States Code and Its Predecessors” section.

To determine which law created your U.S. Code section, and which law or laws may have amended the section over the years, you will want to look to the very end of the U.S. Code section for a series of citations enclosed in parentheses.  This group of citations is called a “source credit” or “source note,” and it lists all of the laws that have affected or created your U.S. Code section.  Each source credit will be laid out chronologically, with the first citation giving information about the public law that gave rise to the U.S. Code section, and each subsequent citation (separated by a semicolon) providing information about the public laws that amended the U.S. Code section.[1]

We want to be sure to note that, if you choose to use a free online resource for tracing purposes, there might not always be source credit information available.  As such, we suggest using the United States Code page provided by the Office of the Law Revision Counsel of the U.S. House of Representatives (OLRC), the organization that publishes the official U.S. Code.  This website not only provides source notes, but even provides a link to the source note at the top of each U.S. Code section.  In addition to the source note, the ORLC website provides an “Amendments” note after each U.S. Code section that will typically list how each subsection of the U.S. Code section was changed by each amending public law (organized by year of the amendment).

Using Source Credits to Find Public Laws

After finding the source credit, you will see that each citation listed has at least three pieces of information—a public law number or chapter number, the date the public law was enacted, and a citation to where the public law can be found in the United States Statutes at Large.  The United States Statutes at Large citation lists a number, then the abbreviation “Stat.” and then another number—the first number is the volume number, and the second number is the page on which the pertinent section of the public law begins.

As specified in “Federal Statutes: A Beginner’s Guide,” free online access to the United States Statutes at Large is determined by when the public law was passed.  For public laws passed before 1875, you can visit our A Century of Lawmaking for a New Nation site.   The Constitution Society’s United States Statutes at Large website covers public laws passed from 1875 to the present, but requires that users download the entire Statutes at Large volume that contains the law in which they might be interested.  Finally, for a more user-friendly experience in finding public laws passed from 1951 to the present, we suggest using the FDSys website.  On the right-hand side of the screen, click “Browse All,” and then on the next page, click on the link for “United States Statutes at Large.” The FDSys United States Statutes at Large page allows users to navigate directly to the public law in which they are interested by clicking the “Private Laws” entry under each volume and finding the public law of interest in a chronological list.  For more up-to-the-minute printings of public laws (1995 to the present), you can also select “Public and Private Laws” from the FDSys homepage.

Next Steps

Finding the public laws in the United States Statutes at Large might be the end of the research trail for those interested in how a law has changed over time.  However, many researchers are also interested in the legislative history documents (such as congressional committee hearings and reports, congressional debates, etc.) attached to the bills and resolutions that eventually became these public laws.  To find the pertinent bill numbers for public laws from 1904 to the present,[2] simply look to the first page of the public law as it is printed in the United States Statutes at Large.  To the immediate left or right (depending on whether the public law starts on an even or odd page) of the first section of the public law, there will be information about both the bill number and date of enactment.  For more information about how to use this citation information to find legislative history documents, please see our “Federal Legislative History Guide.

We hope this Research Guide is helpful for you as you complete your federal legislative research.  If you have any research questions, please contact us via our Ask a Librarian service.

[1] Note that, if the U.S. Code title is a positive law title, there may also be “Historical and Revision Notes,” which “specify the laws that formed the basis of sections that were included in the title when the title was first enacted into positive law. The first act in the source credits for such a section is the act that enacted the title into positive law” (for more information about notes and positive law codification in the U.S. Code, see

[2] To find the bill numbers related to public laws passed before 1904, we suggest using Eugene Nabors’ Legislative Reference Checklist: The Key To Legislative Histories From 1789 To 1903.

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